应变和电场调控HfSe_(2)/PtSe_(2)异质结的电子结构

Tuning the electronic properties of HfSe_(2)/PtSe_(2) heterostructure using electric field and biaxial strain

本团队通过基于密度泛函理论的第一性原理方法,系统地研究了HfSe2/PtSe2范德瓦尔斯异质结(van der Waals heterostructures,vdWHs)的电子性质,包括堆垛方式、层间耦合、应变和外电场的影响.发现堆垛方式可以调节能带对齐类型--AA,AB′和AC′堆垛时为Ⅱ型,AB,AC,AA′则为Ⅰ型.在六种堆垛方式中,AA堆垛是最稳定的,其层间距为2.87A,带隙为1.0 eV,Ⅱ型的能带对齐方式有利于电子-空穴载流子的分离.进一步的计算表明,HfSe_(2)/PtSe_(2)异质结的电子性质可以通过垂直应变和双轴面内应变有效调节:在施加应变或改变层间距后,可以在HfSe_(2)/PtSe_(2)异质结中观察到从Ⅱ型到Ⅰ型能带对齐类型的转变;不仅如此,压缩应变和层间耦合还可以有效调控异质结的带隙大小.本研究将为未来HfSe_(2)/PtSe_(2)异质结在纳米电子及光电设备中的应用提供理论基础.

Herein, using the first-principles methods based on the density functional theory, the electronic properties of HfSe_(2)/PtSe_(2) van der Waals heterostructures(vdWHs) and the influence of stacking patterns, interlayer coupling effect, biaxial strain,and external electric field have been investigated systematically. We found that the stacking patterns could modulate the types of band alignment: AA, AB′and AC′belong to type-Ⅱ band alignment, whereas AB, AC, AA′belong to typeI band alignment. Among these six stacking patterns, the AA stacking pattern was the most stable, with an interlayer distance of 2.87A and a bandgap of 1.0 eV, and the type-Ⅱ band alignment was beneficial for separating electron and hole carriers. Our calculations showed that the electronic properties of HfSe2/PtSe2 vdWHs could be effectively modulated via vertical strain and biaxial strains: an interesting transition from type-Ⅱ to type-Ⅰ band alignment was observed in HfSe_(2)/PtSe_(2) vdWHs upon applying vertical or biaxial strains. Moreover, the bandgap of the designed heterostructure could be effectively modified through the compressive strain and interlayer coupling. Our findings will provide a theoretical basis for the potential applications of HfSe_(2)/PtSe_(2) vdWHs designing of multifunctional electronic and optoelectronic devices.